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M2M Biochemistry and molecular biology > DNA Replication LO > Flashcards

DNA Replication LO Flashcards

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1
Q

what does semi-conservative mean?

A

Newly replicated DNA has one parental strand and one daughter strand

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2
Q

what does bidirectional mean?

A

replication begins at a site of origin and simultaneously moves out in both directions from this point

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3
Q

how many sites of origin do prokaryotes have?

A

1

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4
Q

how many sites of origin do eukaryotes have?

A

multiple

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5
Q

What is a replication fork?

A

site at which DNA synthesis is occurring

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6
Q

what do origin binding proteins do?

A

recognize and bind onto origins of replication

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7
Q

what types of nucleotides are origins of replication rich in?

A

A and T

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8
Q

what do helicases do?

A

unwinds DNA ahead of the replication fork by breaking hydrogen bonds between strands

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9
Q

what do single-strand binding proteins do?

A

bind to each single strand of DNA and hold it in single stranded conformation

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10
Q

What do topoisomerases do?

A

prevent extreme supercoiling of parental helix that would result as a consequence of unwinding at replication fork

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11
Q

how do topoisomerases prevent supercoiling?

A

break and rejoin DNA strands

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12
Q

what is important about DNA gyrase in prokaryotes?

A

can be inhibited by quinolones in treatment of disease

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13
Q

which direction does DNA synthesis proceed?

A

5’ - 3’

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14
Q

how does DNA polymerase work?

A

adds deoxyribonucleotides to the 3’ hydroxyls of RNA primers and subsequently to ends of growing DNA strands

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15
Q

what does a primase do?

A

catalyzes the addition of RNA primer to begin replication

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16
Q

what are the 2 types of DNA polymerases in prokaryotes?

A

DNA pol I and DNA pol III

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17
Q

what is the major replicative enzyme for DNA and why?

A

DNA pol III because it has a sliding clamp that keeps it attached to the DNA template

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18
Q

what does DNA pol I do?

A

mediates replacement of RNA primers with DNA

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19
Q

through which 3 processes does DNA pol I work?

A

a. 5’ - 3’ exonuclease activity for RNA primer removal
b. 3’ - 5’ exonuclease activity for proofreading
c. 5’ - 3’ DNA polymerase activity

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20
Q

what is the function of DNA Pol III

A

it is the major replicative enzyme in DNA synthesis

21
Q

why is DNA pol III the major replicative enzyme?

A

because it has a sliding clamp which keeps it attached to the DNA over a long distance

22
Q

what are the 3 DNA polymerases in eukaryotes?

A

Pol α Pol δ and Pol ε

23
Q

what is the function of DNA pol α?

A

synthesizes the first 20 DNA nucleotides after the RNA primer

24
Q

what types of activity are located in DNA pol α? (2)

A

primase activity and DNA polymerase activity

NO PROOF READING

25
Q

which polymerase performs lagging strand synthesis in eukaryotes?

A

Pol δ

26
Q

which polymerase performs leading strand synthesis?

A

Pol ε

27
Q

what serves as the primer for DNA polymerase in cells?

A

RNA

28
Q

what enzyme places the RNA primer?

A

primase

29
Q

what is the classification of primase?

A

DNA-dependent RNA polymerase

30
Q

in relation to the replication fork, which direction does the leading strand replicate?

A

towards the replication fork

31
Q

in relation to the replication fork, which direction does the lagging strand replicate?

A

away from the replication fork

32
Q

what is the name for the short sequences of DNA located on the lagging strand of DNA replication?

A

okazaki fragments

33
Q

are okazaki fragments longer in eukaryotes or prokaryotes?

A

prokaryotes (1000-2000 bp)

eurakryotes (100-200 bp)

34
Q

how are RNA primers removed?

A

through 5’-3’ exonuclease

DNA pol I in E. coli

35
Q

what does DNA Pol I require on the DNA strand to start DNA synthesis?

A

3’ -OH primer (RNA)

36
Q

which enzyme joins okazaki fragments together?

A

DNA ligase

37
Q

DNA ligase joins which 2 groups together?

A

3’ hydroxyl group with 5’ phosphate group of 2 polynucleotide chains

38
Q

Why is fidelity of replication so high?

A
  1. hydrogen bonds between bp
  2. geometry of AT and CG in active site of polymerase
  3. proofreading through 3’-5’ exonuclease activity
  4. post-replication repair process
39
Q

what is reverse transcription and what enzyme performs this process?

A

synthesis of RNA to DNA

reverse transcriptase

40
Q

what is reverse transcriptase categorized as?

A

RNA dependent DNA polymerase

41
Q

what is the genetic material in retroviruses?

A

RNA

42
Q

what enzyme in eukaryotic cells has reverse transcriptase activity?

A

telomerase

43
Q

what is the job of telomerase?

A

to restore the ends of chromosomes (telomeres) in human cancer and stem cells

44
Q

how does telomerase work?

A

uses RNA template and reverse transcriptase activity to restore telomeres

45
Q

what is the “end replication problem”?

A

leading strand can be synthesized to the very end but lagging strand cannot. This causes shortening of telomeres in cells

46
Q

what happens when telomeres become too short after many round of replication?

A

cell death

47
Q

in what types of cells is telomerase activity repressed?

A

normal somatic cells

48
Q

why is telomerase a potential target in anti-cancer drugs?

A

because telomerase is not repressed in cancer cells, telomeres continue to be restored and thus cell death never occurs

M2M Biochemistry and molecular biology (19 decks)

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